Large, prefabricated structural elements such as beams are widely used in modern construction. These elements, which are typically cast in one piece from concrete, are prestressed under compressive loading so that the elements can bear greater tensile stresses while in service. The prefabricated elements are prefabricated and shipped to the construction site because it is too difficult, time consuming, and expensive to manufacture the elements at the construction site. The prefabricated elements are bulky and heavy and thus are very difficult and expensive to transport. The size of the elements is limited to those that can be economically transported. The elements are also difficult to handle and store at the construction site. These problems are compounded by the fact that the elements are cast solid and thus are very heavy.
The large castings required to make the elements are difficult and expensive to make. Any variations in configuration or even size are very difficult and expensive. Thus, designers and builders have only a limited choice of standard structural element configurations and sizes to work with.